vtraudt

I have to remove the (broken and rattling) cats on my 1996 A4 V6 (12 Valve) automatic.

I would expect this will cause a down stream (B1 S2, B2 S2) O2 sensor code.

On the A4 1.8T, defoulers worked.
On our Cougar, there was a mod (IIRC, a resistor soldered in?) to create a dummy signal.

What do I have to do to prevent a code when removing the cats?

Prospeeder

Somthin like this maybe

http://www.bigdaddiesgarage.com/mini-cat-cel-fix.html

vtraudt

Interesting. I actually did the 'electronic' with 'soldering' modification on our Cougar (test pipe, cat removed). Much cheaper, a bit more work.

Not sure if it works on the Audi, though, and what components need to soldered in to trick the O2 sensor.